Through the present, several techniques have been developed to deliver drugs into the body. Of these, the transdermal delivery of drugs employs injections, ointments, patches, or the like. Injections produce prompt drug effects since a needle is inserted into the body to delivery drugs. Injections are an effective way to deliver drugs due to the delivery of drugs into tissues in the body, such as blood or muscles, and thus are used in various fields. However, the injection causes strong irritation and wounds to the skin, which are accompanied by pain. Moreover, the wounds may bring about further infection, and injections can only be given by experts.
Microneedles are drug delivery systems which are designed in order to solve the above problems. Drugs are delivered into the body through only minimum invasion using microneedles.
Of these, as for a biodegradable microneedle, a microneedle composed of a polymeric material is disposed on a patch, and attached to the skin together with the patch. After the patch is attached, the polymeric material is dissolved through a reaction with body water at body temperature, and here, drugs in the polymeric material are released.
However, this biodegradable microneedle is attached onto the skin in a patch type until the whole polymeric material is dissolved and the loaded drugs are all delivered. Thus, the time of application of the patch inhibits the activity of a user and causes a continuous feeling of irritation. Due to these, timing of application of the biodegradable microneedle is recognized as a limitation, and thus there is a need for a technology to overcome this.
Moreover, the limitation of the timing of application of the patch also causes a limitation of the drug deliverable time of the biodegradable microneedle. While normal drugs need to be continuously delivered into the body at a predetermined quantity, the biodegradable polymeric material has difficulty in drug delivery control after the whole biodegradable polymeric material is dissolved. Thus, the biodegradable microneedle patch is required to be continuously applied. Accordingly, the development of a technology of drug release control through implantation of the biodegradable microneedle is urgently needed.
In addition, in cases where the biodegradable microneedle using a patch is applied to the skin, it is difficult to deliver drugs into wrinkled or corrugated skin. In cases of the wrinkled human skin, the motion of the human body causes movement of the patch, resulting in the detachment of the biodegradable microneedle from the skin, and thus it is impossible to deliver drugs effectively. Also in cases of the corrugated human skin, the biodegradable microneedle cannot completely invade when the patch is applied, due to elasticity of the patch itself.
Meanwhile, the biodegradable microneedle is manufactured by a fine molding method, a drawing method, or a blowing method. All of the above methods for manufacturing the biodegradable microneedle employ mixing a biodegradable polymeric material and drugs. Basically, the biodegradable microneedle is manufactured by preparing a viscous solution in which a biodegradable polymeric material and drugs are mixed, molding a microneedle from the viscous solution, and solidifying the molded material to have a shape and hardness of the microneedle.
Therefore, a solution form in which all the drugs are mixed with the biodegradable polymeric material is used for molding. However, this brings about physical and chemical interactions between the polymeric material and the drugs, causing the degradation in drug activity and the loss of stability.
Additionally, there is a limitation in the kind of drug that can be loaded due to the use of solvent. For example, a hydrophobic drug cannot be used to prepare a solution since it is not mixed with a hydrophilic polymeric material that is mostly used, and thus it is impossible to mold a biodegradable microneedle. Due to this, the biodegradable microneedle, which is manufactured based on a hydrophilic polymeric material for dissolution in the body, has a limitation of not loading a hydrophobic drug.
In addition, the manufacturing process of the biodegradable microneedle necessarily involves a drying step of solidifying a solution to allow the microneedle to have a shape and hardness.
The drying step causes the destruction of the drug structure. The moisture contained in the drug is lost during the drying step, and the drug loses a hydrogen bond with a water molecule, which maintains the drug structure. This causes the destabilization of the drug and the destruction of the drug structure. Also, the drying induces the structural change in the polymeric material, and this change also influences the destabilization of the drug structure.
Due to the above limitations, the existing methods for manufacturing a biodegradable microneedle have a limitation in the kind of loadable drug and the maintenance of drug stability.
Further, when a solution is prepared by mixing a biodegradable polymeric material and drugs, the biodegradable microneedle fails to have sufficient hardness in cases where a predetermined quantity or more of drug is loaded. In those cases, the biodegradable microneedle has difficulty in delivering a predetermined quantity or more of drug.
As described above, the drug delivery techniques have been developed recently, but there are still limitations in delivering insoluble drugs, delivering unstable drugs, storage and distribution, and the like. Accordingly, there is a need for a technology to overcome these limitations, and many studies are being conducted in the corresponding fields.
Throughout the entire specification, many papers and patent documents are referenced and their citations are represented. The disclosures of cited papers and patent documents are entirely incorporated by reference into the present specification, and the level of the technical field within which the present invention falls and details of the present invention are explained more clearly.